Study on Mechanical Properties of Sand-Mudstone Interbedded Rock Samples with Different Confining Pressures and Dip Angles

In order to study the mechanical properties of the interbedded samples mass of sand and mudstone, the mechanical parameters of sandstone and mudstone were first obtained through laboratory tests, the microscopic parameters of sandstone and mudstone were calibrated by PFC^2d software, and then the sandstone-mudstone interceded rock samples were tested in triaxial compression numerial test under different confining pressure and dip angles conditions. The influences of confining pressure and dip angle on the mechanical properties and failure characteristics of sand-shale interbedded rock samples are analyzed. The results show that: (1) Under the same confining pressure, with the increase of the dip angle of rock formation, the compressive strength, elastic modulus and cohesion all tend to decrease first and then increase, and the minimum value is when the rock formation dip angle is 60°. As the confining pressure increases, the axial strain also increases accordingly. (2) The mutation point of the number of cracks during the loading process of the specimen corresponds to the elastic, plastic and failure characteristic points of the stress-strain curve, and the proportion of the number of tensile cracks to the total number of cracks is greater than that of shear cracks. (3) Under the influence of rock formation dip angle and confining pressure, the failure modes of sand-mudstone interbedded rock samples can be divided into three types: tension shear failure, shear slip failure along the bedding plane, slip failure and tension shear failure Simultaneous composite failure. The research conclusions can provide reference for the deformation and stability analysis of related engineering of sand-shale interbedded rock mass.